Het voorspellen van de gevoeligheid van kinderleukemiecellen voor proteasoomremmers

Introduction. For children with relapsed acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), there is a need for new therapeutic drugs. Bortezomib (BTZ) is a reversible proteasome inhibitor currently being tested in clinical trials for children with relapsed ALL and AML. BTZ-related toxicity and emergence of resistance has initiated the development of several new irreversible proteasome inhibitors. The aim of this research project is to investigate whether pediatric leukemia cells are sensitive to BTZ and new generation proteasome inhibitors (carfilzomib, ONX 0912 and ONX 0914), and to identify factors that will predict responsiveness of children on treatment with proteasome inhibitors. Methods. Leukemic blast cells of 29 ALL and 10 AML patients were analyzed for sensitivity to BTZ, carfilzomib, ONX 0912, ONX 0914, and the glucocorticoid dexamethasone by MTT cytotoxicity assays. Additionally, protein expression of the functionally-active proteasome subunits was determined by Western blotting and ProCISE, and correlated to proteasome inhibitor sensitivity. Results. ALL cells were significantly more sensitive to all proteasome inhibitors and dexamethasone than AML cells. Besides this, expression of constitutive proteasome subunits relative to immune proteasome subunits was significantly higher in AML cells than in ALL cells. The ratio of immune/constitutive proteasome subunit expression correlated with sensitivity of ALL cells for ONX 0914, and of AML for BTZ and carfilzomib sensitivity. Conclusion. Expression levels of proteasome subunits can be of predictive value how a patient may respond to proteasome inhibitors. As such, this research contributes to a more personalized therapy for children with leukemia in the future.